Update: The $500 model appears to be sold out in most areas, but the UN55KU6290 is on sale for $550. It has a different remote than the 6300, but it does have Bluetooth and all of the same ports.
The most popular TV we posted last year (and the one I bought myself) was the Samsung UN55KU6300, which includes a 4K panel, smart apps, and even HDR. We saw it get as low as $550, but the nearly identical UN55KU6270 is now on sale for just $500.
The only differences, so far as I can tell, are a couple fewer ports and no Bluetooth connectivity. If you can live without those, you’d be hard pressed to find a better picture for this price.